LATEST PLEISTOCENE SEDIMENTATION ON THE NJ UPPER SLOPE: GRAIN SIZE ANALYSIS OF SITE 1073A

Glaciation had a significant impact on the NJ continental margin. Although erosional processes dominated on the shelf, the continental slope was a site of deposition. This study evaluates the timing and nature of sedimentation on the latest Pleistocene New Jersey Ocean Drilling Program (ODP) Leg 174 slope Site 1073A (640 m water depth). Cores 1 and 2 were sampled 10cm intervals; samples were dried, rehydrated, and sieved (63µm); the fine fraction was analyzed with the Micromeritics Sedigraph 5120 for mass frequency of silt, clay, 12 phi and 13 phi.

Cores 1 and 2 the weight percent sand increases up core overall, and % silt, while variable, decreases up section from ~80% to ~40%. The % 12 phi generally follows the % clay, but the very finest grains (%13 phi) does not. Observations of the sediments in the >150 fractions indicates a change in sediment source around 2.84 mbsf; below the grains are predominantly quartz, and above it is oxidized mud fragments. This does not correlate with large changes in % silt or clay, and may be related to post-glacial depositional patterns on the shelf.